diff --git a/programs/ssl/ssl_mail_client.c b/programs/ssl/ssl_mail_client.c
index 74d5d72700..0f2b32ddcf 100644
--- a/programs/ssl/ssl_mail_client.c
+++ b/programs/ssl/ssl_mail_client.c
@@ -19,8 +19,8 @@
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 
-/* Enable definition of hostname() even when compiling with -std=c99. Must be
- * set before config.h, which pulls in glibc's features.h indirectly.
+/* Enable definition of gethostname() even when compiling with -std=c99. Must
+ * be set before config.h, which pulls in glibc's features.h indirectly.
  * Harmless on other platforms. */
 #define _POSIX_C_SOURCE 200112L
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 084da59f49..34d6494707 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -16,7 +16,7 @@ if(NOT PERL_FOUND)
 endif()
 
 # Enable definition of various functions used throughout the testsuite
-# (hostname, strdup, fileno...) even when compiling with -std=c99. Harmless
+# (gethostname, strdup, fileno...) even when compiling with -std=c99. Harmless
 # on non-POSIX platforms.
 add_definitions("-D_POSIX_C_SOURCE=200809L")
 
diff --git a/tests/Makefile b/tests/Makefile
index d65cd93a25..37e8cbcbad 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -12,6 +12,11 @@ LOCAL_LDFLAGS = -L../library 			\
 		-lmbedx509$(SHARED_SUFFIX)	\
 		-lmbedcrypto$(SHARED_SUFFIX)
 
+# Enable definition of various functions used throughout the testsuite
+# (gethostname, strdup, fileno...) even when compiling with -std=c99. Harmless
+# on non-POSIX platforms.
+LOCAL_CFLAGS += -D_POSIX_C_SOURCE=200809L
+
 ifndef SHARED
 DEP=../library/libmbedcrypto.a ../library/libmbedx509.a ../library/libmbedtls.a
 else